In order for a coastal city to establish a steady trade, fishing, or other shipping industry, the city must have a harbor, a body of water that protects ships from waves and high winds. Although natural harbors exist, these often require extensive dredging and construction to accommodate and protect large vessels.

The Canton System was an attempt by the Chinese Qing Dynasty to control the influence of foreign traders within their borders. Foreign nations were allowed no direct access to the Chinese populace, instead trading through proxies at various harbors throughout China. Macau and Canton (now called Guangzhou) were the two main Canton harbors.

A sydharb is a unit of measurement employed for large bodies of water. Its name comes from the approximate size of Sydney Harbor in Australia. One sydharb is roughly 560 gigaliters or 560,000,000,000 liters.